Resin-bonded abrasive tools with molybdenum metal filler and molybdenum disulfide lubricant

ABSTRACT

High ratios of metal removed to abrasive tool wear are achieved when resin-bonded diamond or cubic boron nitride abrasive tools include in the bond from 10 to 60 percent by volume of silver, silver coated copper, or copper powder in the presence of from 5 to 30 percent by volume of a solid lubricant. Other fillers such as finely divided metal oxides or carbide such as silicon carbide may be present in an amount of from 0 to 40 percent by volume, depending upon the total content of metal and lubricant. The diamond wheels or tools of this invention are particularly suitable for the dry grinding of carbide tools. The cubic boron nitride wheels employ metal clad boron nitride abrasive particles and are particularly suitable for the dry grinding of hard steel tools, that is, high speed steels such as T15, M2, M3, and M4. Solid lubricants useful in this invention icnlude organic polymers such as polytetrafluoroethylene, fluorinated ethylene polymers, chlorinated hydrocarbon, fluorinated ethylene propylene, polyethylene styrene-butadiene, acrylonitrilebutadiene-styrene, polyurethane, polyformaldehyde, polycarbonate, and nylon and inorganic crystalline solids such as boron nitride, tungsten disulfide, graphite, metal coated graphite, molybdenum disulfide, niobium diselenide tungsten diselenide, and fluorinated graphite.

United States Patent [1 1 Sioui et al.

[4 1 Feb. 25, 1975 RESIN-BONDED ABRASIVE TOOLS WITH MOLYBDENUM METALFILLER AND MOLYBDENUM DISULFIDE LUBRICANT [75] Inventors: Richard H.Sioui, Holden; Harvey M. Cohen, Randolph, both of Mass.

[73] Assignee: Norton Company, Worcester, Mass.

[22] Filed: Apr. 25, 1973 [21] Appl. No.: 354,460

Related U.S. Application Data [60] Division of Ser. No. 163,976, July19, 1971, Pat. No. 3,779,727, which is a continuation-in-part of Ser.No. 61,905, Aug. 7, 1970, abandoned.

[52] U.S. Cl. 51/298, 51/295 Primary E.\'aminerDonald J. ArnoldAttorney, Agent, or Firm -Rufus M. Franklin [57] ABSTRACT High ratios ofmetal removed to abrasive tool wear are achieved when resin-bondeddiamond or cubic boron nitride abrasive tools include in the bond from10 to 60 percent by volume of silver, silver coated copper, or copperpowder in the presence of from 5 to 30 percent by volume of a solidlubricant. Other fillers such as finely divided metal oxides or carbidesuch as silicon carbide may be present in an amount of from 0 to 40percent by volume, depending upon the total content of metal andlubricant. The diamond wheels or tools of this invention areparticularly suitable for the dry grinding of carbide tools. The cubicboron nitride wheels employ metal clad boron nitride abrasive particlesand are particularly suitable for the dry grinding of hard steel tools,that is, high speed steels such as T15, M2, M3, and M4. Solid lubricantsuseful in this invention icnlude organic polymers such aspolytetrafluoroethylene, fluorinated ethylene polymers, chlorinatedhydrocarbon, fluorinated ethylene propylene, polyethylenestyrene-butadiene, acrylonitrilebutadiene-styrene, polyurethane,polyformaldehyde, polycarbonate, and nylon and inorganic crystallinesolids such as boron nitride, tungsten disulfide, graphite, metal coatedgraphite, molybdenum disulfide, niobium diselenide tungsten diselenide,and fluorinated graphite.

1 Claim, 3 Drawing Figures RESIN-BONDED ABRASIVE TOOLS WITH MOLYBDENUMMETAL FILLER AND MOLYBDENUM DISULFIDE LUBRICANT This is a division, ofapplication Ser. No. 163,976, filed July 19, 1971, now U.S. Pat. No.3,779,727, which was a continuation-in-part of application Ser. No.61.905. filed Aug. 7, 1970, now abandoned.

FIELD OF THE INVENTION This invention relates to abrasive tools, inparticular grinding wheels and coated abrasive belts, containing thehardest known abrasives, diamond and cubic boron nitride which, whenmetal coated diamond grit is the primary abrasive are particularlysuitable for the dry grinding of cemented carbide tool material (e.g.cemented tungsten carbide), and when metal coated boron nitride grit isthe primary abrasive are particularly suitable for grinding hard toolsteels such as T15, M2, M3. and M4.

THE DRAWINGS FIG. 1 shows a perspective view of a grinding element suchas produced according to the present invention.

FIG. 2 shows a perspective view of the grinding element of FIG. Imounted for use.

BACKGROUND OF THE INVENTION Improvement of resinoid bonded diamond (orcubic boron nitride) abrasive tools has been recently achieved by theuse of metal clad diamond grit or by the use of metalclad cubic boronnitride grit. The present inventors have disclosed the use of finelydivided graphite in such tools in US. application Ser. No. 876,655.filed Nov. 14, 1969, now US. Pat. No. 3,664,819, to improve,significantly the performance in dry grinding. In particular thisapplication relates to the use of molybdenum metal filler withmolybdenum disulfide solid lubricant.

SUMMARY OF THE INVENTION The present invention involves modifying thebond of resinoid bonded abrasive tools, containing metal clad diamond orcubic boron nitride, by inclusion of from 10 to 60 percent by volume,preferably 30 to 50 percent by volume of the total of bond and fillers(exclusive of the metal clad abrasive) of molybdenum, and from 5 to 30percent. preferably to percent of molybdenum disulfide.

The components of the grinding elements or tools of the presentinvention will now be discussed in detail. The Bond Any of the knownsynthetic resins useful in making coated or bonded abrasives may beemployed in the present invention. Obviously, strength and heatresistance are necessary properties. The wellknown cross linked resinssuch as phenol-aldehyde resins, melamine-aldehyde resins, urea-aldehyderesins, polyester resins, and epoxy resins, including the epoxynovolacs, may all be used and conventional modifiers and plasti cizersmay be used. Part of the filler content may consist of conventionalparticulate tillers such as silicon carbide. Fairly recently, newessentially linear polymers as well as thermoset polymers (such asthermoset polymers disclosed in French Pat. No. 1,455,514) have beenintroduced which have utility in bonding abrasive grains. These resins,like the crosslinked resins discussed above, are infusible, as opposedto the more common thermoplastic linear polymers having definitesoftening ranges and which are reversibly softenable. Examples of suchresins, having utility in making abrasive tools, are given in U.S. Pat.No. 3,329,489 (polybenzimidazole), and US. Pat. Nos. 3,295,940 and3,385,684 (polymides). Polysulfide resins such as disclosed in 1.1.5.Pat. No. 3,303,170 and polypyrrones may also be employed. For use inmaking coated abrasive discs or belts liquid resin systems may bepreferred, while for bonded abrasives solid powdered resins can be used.

The Abrasive One of the preferred features of the present invention isthat the abrasive, diamond grit, or cubic boron nitride, have a metalcoating encapsulating the abrasive grit such that the metal is presentin the coated particle in an amount between 10 and percent, by volume.Uncoated diamonds can be used, however, and tools employing them areconsidered part of the present invention. Metal coated diamonds aredisclosed in Soulard French Pat. No. 1,142,688, Belgian Pat. Nos.683,508 and 698,428, and French Pat. No. 1,522,735. Suitable metalcoatings are copper, silver, nickel, cobalt, molybdenum and, in general,any metal melting above about 500 F which is chemically stable in thegrinding tool. Although, for wet grinding the volume percent of metalcoating can be higher, for dry grinding, to which the tool of thepresent invention is partic ularly directed, the volume percent of metalcoating should be between 10 to 60 percent. by volume.

Coated diamonds are commercially available which have nickel coatingswithin the above range of 10 to 50 percent. by volume, and coppercoatings. within the same range. These coatings can be produced byelectrodeposition on a thin, silver coating produced by chemicaldeposition on the grits. Thus the coatings need not be a single metal,only, and a wide variety of metal coatings are possible and useful inthe present invention. Alloys of the metals are also useful.

The grit size of the abrasive is not relevant to the present invention,but grit sizes of 60 through 320 (based on the uncoated grit) arecommonly used in diamond wheels.

The Grinding Tool Grinding elements according to the present inventionmay be formed by pressing the mixture in a mold of the desired shape.The mold may be heated and the resin may be completely or partiallycured in the mold.

FIG. 1 shows a typical grinding element 10. FIG. 2 shows the grindingelement mounted on a core 20 to produce a straight grinding wheel. FIG.3 shows the element 10 mounted on a cup shaped support to form agrinding wheel commonly referred to as a cup wheel." A suitable materialfor making the support member is an aluminum-filled resin as disclosedin US. Pat. No. 2,150,886. The tool may be molded directly onto thesupport, the support may be molded onto the tool, or the tool may becemented onto the support after fabrication.

For the production of coated abrasive discs or belts, a liquidphenol-formaldehyde resin can be used. A size coat of liquid resinshould be employed after the maker coat, and at least the size coatshould contain the fillers of this invention. The size should be high,that is, it should extend from the maker coat to close to the tips ofthcabrasive so that the fillers in the coat contact the work duringgrinding. The Fillers The required fillers of the present invention are:1 molybdenum present in the bond in the amount of from 10 to 60 percentby volume, preferably 30 to 50 percent, and 2. molybdenum disulfidepresent in the bond in the amount of from to 30 percent, by volume, andpreferably from to 20 percent.

In addition to the metal and dry-film lubricant powder fillers, inertfillers such as silicon carbide may be added to improve the strength ofthe bond or otherwise control its physical properties. Where lowerdiamond concentrations are employed it may be desirable to add suchfillers to reduce the overall bond content of the tool or grindingelement.

SPEClFlC EMBODIMENTS OF THE INVENTION Although this invention isspecific to the use of molybdenum (instead of silver or copper) andmolybdenum disulfide as the lubricant, the following illustrate thebroader aspects of the invention as claimed in US. Pat. No. 3,779,727.

Normal process steps, conventional in the art, are

used to fabricate the wheels, discs, or belts according to the presentinvention.

A preferred example of a bond mix for making a bonded abrasive ring formounting on a backing element, such as shown in the drawing is asfollow:

PHENOLIC BOND EXAMPLE cure can be carried out in an air atmosphere ovenfor 24 hours at 175 C. Control of the temperature of the final cure iseffective, as is well known in the art, in

'controlling the hardness or grade of the bond which 5 may differdepending upon the specific application.

The cured abrasive element is attached to a core or holder, as inconventional in the art, to produce a grinding tool such as shown inFIGS. 2 and 3 of the drawing. In the tabulated examples below, cup type10 wheels were employed of the dimensions and standard indicated. Allthe tests were run dry (no liquid coolant).

Where other resin systems are employed than the phenolic bond givenabove, it is known in the art that different curing or processingtemperatures may be required. For example, in the case of the polymideresins, typical fabrication conditions would be a pressure of 10 tonsper square inch, and a hold at 270 C for minutes. No post cure isrequired. A commercial polymide available from Rhone-Poulenc, identifiedas P.I.- M33A, cured under these conditions, and containing 50 percentsilver filler and 10 percent polytetrafluorethylene as fillers, gave agrinding efficiency of 202 7 percent or 102 percent above the controlwheel, in a test similar to that of Table l. A second test with adifferent polymide identified as P.l.-M33B. gave a grinding efficiencyof 293 percent under identical conditions where 40 percent silver and 10percent TFE fillers were s -H...

The following test was made on wheels made according to the PhenolicBond Example given above, the amounts of fillers and resin, however,being varied as indicated. The wheels were cup wheels, 6A9 type, 4 35inches X 1% inches X 1% inches. The diamond was Pawdvrsdphenul-flldehyde coated with 56 weight percent nickel and was 150 gritpre-polymcr (BRP 5980 available from Union Carbide Corporation) 173 45.2(Pncodtedl and the Wheels Contamed perfem which includes 9%hcxamcthylene diamond by volume. The work ground on a mod1f1ed W' e R ilby surface grinder was a cemented tungsten carbide, the WClg O 1mc1s 21e Silver powder (Mm Refining 58.6 4O unlt mfeed was 2.5 m1ls. G r1nd1ngcond1t1ons and the ('6. N0. (-18) work p1ece were the same for all thewheels. The first bWfl F I wheel listed was a standard commercial wheelcontain- (Liquul Nitrogen Processing (0. 6.1) 10 NO. 'r1.-| 15) mgpercent by volume of SlllCOl'l carbide 1n the bond. $111 6 Carbide (8 gl 2' 177 Table 1 gives the results. The wheel no." is for identificationpurposes. G is the grinding ratio or grinding effi- TABLE l Filler Level(74 of bond) Wheel No. G P 7cG /rP SiC Ag TFE in making a bondedabrasive tool employing the above mix, the abrasive is wet with thefurfural .and the mixture of bond and fillers is added and mixingcontinued to form a homogeneous batch. Sufficient of the mix is thenplaced in, a mold of the desired shape and the mix is hot-pressed toshape. Normally, using the above bond, the tool is then removed from themold and further cured in an oven. Typical molding conditions are apressure of 5 tons per square inch, a temperature of C, and a moldingtime of 20 minutes. The final cent level produces no significantimprovement. But combined, at these levels, the efficiency issignificantly improved and the power is significantly reduced. Bestresults, in this test, were shown with 20 percent silver and 10 percentpolytetrafluoroethylene.The results thus show a synergistic effect whenthe two fillers are employed together in the bond, which would not beexpected from the results obtained when only silver or onlypolytetrafluoroethylene are employed.

The test results given in Table 11 compare the results for wheels ofvarious levels of fillers with a standard wheel like that of Table l,but containing a slightly higher level of silicon carbide filler. Thediamond was 150 grit, nickel coated, except for the diamond in the lasttwo wheels which was copper coated in the amount of 50 weight percent.The infeed was 2.5 mils on cebut a different cemented tungsten carbide,sample was employed in the workpieces. This test evaluated silvercontents of 10 to 20 percent with no lubricants and silver contents of10 to 20 percent combined with 15 to 25 percent graphite.

Table IV gives the results of a test wherein silver contents of 30 to 50percent, with a solid film lubricant filler, were compared to a standardwheel and to a wheel containing graphite only. As in the previous tests,the wheels were all run on the same sample of carbide and under the sametest conditions. The infeed was 2.0 mil. The diamond was present in theamount of 1 1 percent by volume in the wheels, instead of 17 percent asin the previous tests, and was nickel clad, except for the diamond inwheel 84 which was copper clad.

TABLE IV Filler Levels Wheel No. C P %G %P Ag TFE Graphite SiC 47(Control) 17.4 199., 100 0 0 Q 7 51 22.6 765 130 75 O 2O 82 63.6 1135365 111 4O 10 0 O 83 79.8 1190 459 116 50 10 0 0 84 67.8 925 390 90 5010 O 0 85 44.0 840 253 82 30 0 0 86 43.1 840 82 4O 0 7 2O 0 mentedtungsten carbide workpieces. The carbide ma- At 2.5 mil. infeed therelative results were similar exterial and the grinding conditions werethe same for all cept that wheels 84 and 86 were unsatisfactory underwheels. the higher infeed in that they loaded, chipped, and

TABLE 11 Filler Level Whccl No. G P 700 %P SiC Ag TFE 18664 47.6 1425100 100 0 0 18665 78.5 1120 165 79 10 20 10 18666 89.6 975 188 68 5 2O15 18667 87.7 1180 184 83 5 25 10 18668 95.2 1020 200 72 0 25 15 18669147.5 1280 312 90 O 30 15 18670 108.5 1090 228 76 0 3O 15 18671 91 1120191 79 1O 20 10 18673 75.3 960 158 67 5 20 15 The conclusions drawn fromthis test are that the optimum silver content is over 30 percent, 15percent TFE is better than 10 percent from the standpoint of powerdrawn, and nickel and copper coated diamond are similar in performancewhen 20 percent silver filler is employed.

The following results were performed on a different, somewhat more rigidmachine than the previous tests. Otherwise the test conditions wereessentially the same,

In the following test silver filler was compared with silver coatedcopper. The wheels all contained 1 1 percent by volume of diamond, andthe diamond was nickel clad. The unit infeed was 2.0 mils. The results eeas o ows TABLE V Wheel No. G P %G %P Ag TFE Ag on CU SiC Control 17.8875 100 100 0 0 0 35 950 28.9 825 162 94 50 15 0 0 951 29.6 800 166 9145 15 O 0 956 29.2 750 164 86 0 15 45 0 TABLE 111 Filler Level Wheel No.0 P G '70P %SiC 7m %Graphite 18713 (Control) 26 1075 11 100 40 0 0Although this test showed that Ag and Ag coated Cu are equivalent, moresensitive testing has indicated the superiority of Ag over Ag coated Cu.

In the grinding of high-speed steels, wheels employcopper with variousfillers, as listed below in Table VIII and grinding efficiencies lowerthan the standad control wheel were achieved with nickel, molybdenum,iron, tin, and aluminum fillers.

ing metal clad 150 grit cubic boron nitride were com- 5 Throughout thespecification the volume percent of pared with various filler contents.The unit infeed was fillers in the bond means the parts of filler perhundred 2.0 mils. and the wheels were the same shape and diparts oftotal bond solids, including fillers, but not inmenslons as m the testsreported above. eluding abrasive particles and not including the metalThe filler content of the wheels was as follows: cladding on theabrasive.

l TABLE W What is claimed is:

Wheel No. SiC Al Q- Ag TFE Graphite g 8 1. An abrasive tool comprisingparticles selected 838 0 0 U '5 from the group consisting of metal claddiamond or 8313 28 0 0 0 20 metal clad cubic boron nitride bonded at atleast one 853 O 0 40 0 surface thereof, the bonding material being asynthetic TABLE VIII Wheel No. G 720 P 7r! Metal Lubricant 19083 42 4101200 120 A EN 19076 39.5 383 1150 115 A TFE 19086 35.9 348 1250 125 A ws19229 30.8 299 1350 135 Ag BN Nickel Coated 19089 30.5 296 1400 140 AgGraphite 19085 27.9 271 1150 115 Ag Mus 19088 27.8 270 H H5 AgPolyethylene 19084 26.3 255 1350 135 Ag Nbse 19087 20.2 196 1100 110 Agwse 19090 15.1 147 1050 105 Mo M s 19077 14.4 140 1150 115 Cu TFE 1923111.9 116 1000 100 M0 M05. 19257 10.7 104 850 Graphite 19252 10.3 1041000 100 Control Wheel 35% siC 19078 9.3 950 i TFE 19082 7.5 73 800 80Mo TFE 19228 6.4 62 850 85 Mo TFE l908l 5.8 56 850 85 Fe TFE I9079 5.452 900 90 Al TFE 19080 4.4 43 800 80 Sn TFE 19230 3.2 31 750 75 Al TFEThe test results on M3, M43, and T15 high-speed 40 resin binder butcharacterized in that it contains from steel workpieces were as follows:10 to 60 percent by volume, of molybdenum metal TABLE Vll Wltccl M3 M43Tl5 N0. (1 1 7m '54 P (i P n (1 .40 G P Z-(i 711 Based on the mostreproduceable testing methods, filler and from 10 to 30 percent, byvolume, of molybgained from the above tests, a variety of metal andsolid denum disulfide. lubricant combinations were employed. Grindingeffi- 55 2 ciencies of at least 40 percent above the standard wereachieved with the metal silver, copper, or silver coated UNITED STATESPATENT Q EIEE @ERTEHQATE 0F CURRECTIQN PATENT NO. i 3,868, 232 DATEDFebruary 25, 1975 INVENTOMS) Richard Hc Sioui and Harvey M, Cohen It iscertified that error appears in the ab0ve-identified patent and thatsaid Letters Patent are hereby corrected as shown below.

TABLE IV, line 1; under P "100" should read 1025 under %P O should read100 ggncd and gealed this fif h Day of August1975 [SEAIL] A ttest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer ('rmlmissimzcr ofParents and Trademarks

1. AN ABRASIVE TOOL COMPRISING PARTICLES SELECTED FROM THE GROUPCONSISTING OF METAL CLAD DIAMOND OR METAL CLAD CUBIC BORON NITRIDEBONDED AT AT LEAST ONE SURFACE THEREOF, THE BONDING MATERIAL BEING ASYNTHETIC RESIN BINDER BUT CHARACTERIZED IN THAT IT CONTAINS FROM 10 TO60 PERCENT BY VOLUME, OF MOLYBDENUM METAL FILLER AND FROM 10 TO 30PERCENT, BY VOLUME, OF MOLYBDENUM DISULFIDE.